UltraCAD

Introduction It s no news that the band pass requirements for power sys-tems on PCB s are increasing and that power supply imped-ance requirements are getting tighter. Bypass capacitor fabri-cation and assembly techniques are improving and pushing higher the normal self-resonant frequencies we have to deal with. ESR s (equivalent series resistance) are decreasing, pushing further down the floor of the power supply impedance curve. All this has created increased debate as to how to take advan-tage of this higher self-resonant requency and lower ESR. One argument is that lower ESR is thoroughly beneficial. Another is that, while lower ESR lowers the impedance at the mini-mum points, it also increases it at the maximum ( anti-resonant ) points, and therefore lower ESR is not necessarily beneficial. Some argue for system designs that incorporate a well defined number of high quality (precise self-resonant fre-quencies and low ESR) capacitors with carefully chosen self-resonant frequencies.

Impedance at “Anti -resonance” If we let X1 = -X2, then Im(Z) goes to zero, by definition. This is the “anti -resonant” point bet ween Fr1 and Fr2.

Loading..

Tags:

  Ultracad

Information

Related search queries